Networking has long featured a variety of tunneling, tagging, and other encapsulation mechanisms. However, the advent of network virtualization has caused a surge of renewed interest and a corresponding increase in the introduction of new protocols. There are a large number of protocols in this space, including Virtual Local Area Networks (VLANs), Multiprotocol Label Switching (MPLS), and Virtual Extensible LAN (VXLAN).
Some of the newer protocols used for virtualization have at least 24 bits of identifier space as a way to partition between tenants. This is often described as overcoming the limits of 12-bit VLANs, and when seen in that context, or any context where it is a true tenant identifier, 16 million possible entries is a large number. However, the reality is that the metadata is not exclusively used to identify tenants. With changing control plane implementations and advancement, there are new requirements that require encoding other information.
Existing tunnel protocols have each attempted to solve different aspects of these new requirements, only to be quickly rendered out of date by changing control plane implementations and advancements. Furthermore, software and hardware components and controllers all have different advantages and rates of evolution.